Does that apply to all uses of "sealant" or just sealant only as the means of closing an opening?
What I am getting at is something I have done many times and never had it rejected either is to put a bead of silicone around a hole then screw a metal plate over a hole (4x4 flat blanks work great up to 3 inch ko size holes).
I did not read code before this reply, but seem to recall there is no requirement that material used to close an opening be listed, just that it provides a closure that is equivalent to the rating of the enclosure, so if it is a raintight enclosure I fail to see how this method doesn't provide raintightness as well as similar metal thickness and strength of the original enclosure. Have many times used a bolt/nut maybe a washer for smaller holes - especially if not a standard KO size. If outdoors and around grain bins - there are hundreds of rubber gasket(-ed) washer head bolts that were left over from the construction of the bin and usually laying on the ground as the bin construction guys drop them all over the place - they seal pretty well. I always pick several up, otherwise they just eventually get buried in the dirt.